1. Field of the Invention
The present invention relates to a structure detection apparatus and method for detecting a specific structure in a medical image, or the like. Further, the present invention relates to a computer-readable recording medium storing a structure detection program.
2. Description of the Related Art
An advance in medical equipment (such as a multi-detector CT for example) in recent years provided high-quality three-dimensional (3D) images that can be used in image diagnosis (diagnosis using images). A 3D image is composed of a multiplicity of two-dimensional (2D) images, and the data amount of the 3D image is large. Therefore, when a doctor uses the 3D image for diagnosis, it takes a long time to find a desired observation region in some cases. Therefore, a method for displaying a whole organ or a lesion in an easily recognizable manner has been attempted to improve the efficiency of diagnosis. In the method, an organ of interest is extracted, and displayed by MIP (maximum intensity projection), VR (volume rendering), CPR (curved planer restoration), or the like. For example, when a cardiac CT image is analyzed, and especially when a coronary artery is analyzed, it is necessary to extract the center path of the coronary artery as a graph structure to obtain a CPR image developed along the path of blood vessels and effective data for diagnosis, such as a stenosed region and the degree of stenosis.
A predetermined structure is automatically extracted from 3D image data, such as volume data (please refer to U.S. Pat. No. 7,646,903 (Patent Document 1) for example). In Patent Document 1, a tree structure is collected, for example, by respiratory tract—respiratory tract matching, or tree structures are collected from structures obtained at different time from each other. Further, a plurality of paths (nodes) are extracted from the collected tree structures, and tree matching (graph matching) is performed by using each of the extracted paths to measure the similarity of the graph structures.
Further, various methods have been proposed in extraction of structures on which matching is performed as described above (please refer to the specification of U.S. Pat. No. 7,346,209 (Patent Document 2) and U.S. Patent Application Publication No. 20080044080 (Patent Document 3) for example). For example, in Patent Document 2, three slice images that are orthogonal to each other are generated from 3D image data, and a specific object is detected based on feature values extracted from the three slice images. In Patent Document 3, a specific structure is detected in a 2D image by machine learning on a target region.
However, when a specific object is detected based on the feature value of image data or the like, as disclosed in Patent Documents 2 and 3, a wrong structure is detected in some cases. Further, in Patent Document 1, matching is not accurate. Specifically, for example, when a blood vessel is narrowed or blocked by a plaque, the plaque region is not recognized as a region of the blood vessel, and not extracted as a candidate point for the blood vessel in some cases. Further, when a coronary artery is extracted, if a vein runs parallel to the coronary artery, the vein may be erroneously detected as the coronary artery.